Viessmann VITOFLAME 300 Operating instructions

Service instructions
for contractors
VIESMANN
Vitoflame 300
Type VHG, 18 to 33 kW
Pressure-jet oil burner
■With oil preheating
■For Vitoladens 300-T and Vitorondens 200-T/222-F
VITOFLAME 300
5777267 GB 8/2019 Please keep safe.

2
Please follow these safety instruc-
tions closely to prevent accidents
and material losses.
Safety instructions explained
Danger
This symbol warns against the risk
of injury.
!Please note
This symbol warns against the risk
of material losses and environmen-
tal pollution.
Note
Details identified by the word "Note"
contain additional information.
Target group
These instructions are exclusively inten-
ded for qualified contractors.
■Work on electrical equipment may only
be carried out by a qualified electrician.
■The system must be commissioned by
the system installer or a qualified per-
son authorised by the installer.
Regulations to be observed
■National installation regulations
■Statutory regulations for the prevention
of accidents
■Statutory regulations for environmental
protection
■Codes of practice of the relevant trade
associations
■Relevant country-specific safety regu-
lations
Safety instructions for working on the system
Working on the system
■Isolate the system from the power sup-
ply (e.g. by removing the separate fuse
or by means of a mains isolator) and
check that it is no longer live.
■Safeguard the system against recon-
nection.
Danger
Hot surfaces can cause burns.
■Before maintenance and service
work, switch OFF the appliance
and let it cool down.
■Never touch hot surfaces on the
boiler, burner, flue system or pipe-
work.
Safety instructions
Safety instructions
5777267

3
!Please note
Electronic assemblies can be dam-
aged by electrostatic discharge.
Prior to commencing any work,
touch earthed objects such as heat-
ing or water pipes to discharge
static loads.
Repair work
!Please note
Repairing components that fulfil a
safety function can compromise the
safe operation of the system.
Replace faulty components only
with genuine Viessmann spare
parts.
Auxiliary components, spare and
wearing parts
!Please note
Spare and wearing parts that have
not been tested together with the
system can compromise its func-
tion. Installing non-authorised com-
ponents and making non-approved
modifications or conversions can
compromise safety and may invalid-
ate our warranty.
For replacements, use only original
spare parts supplied or approved by
Viessmann.
Safety instructions for operating the system
If you smell flue gas
Danger
Flue gas can lead to life threatening
poisoning.
■Shut down the heating system.
■Ventilate the installation site.
■Close the doors to living spaces to
prevent flue gases from spread-
ing.
What to do if water escapes from the
appliance
Danger
If water escapes from the appliance
there is a risk of electric shock.
Switch OFF the heating system at
the external isolator (e.g. fuse box,
domestic distribution board).
Danger
If water escapes from the appliance
there is a risk of scalding.
Never touch hot heating water.
Flue systems and combustion air
Ensure that flue systems are clear and
cannot be sealed, for instance due to
accumulation of condensate or other
external causes. Ensure an adequate
supply of combustion air.
Instruct system users that subsequent
modifications to the building characteris-
tics are not permissible (e.g. cable/pipe-
work routing, cladding or partitions).
Danger
Leaking or blocked flue systems, or
an inadequate supply of combus-
tion air can cause life threatening
poisoning from carbon monoxide in
the flue gas.
Ensure the flue system is in good
working order. Vents for supplying
combustion air must be non-seala-
ble.
Safety instructions
Safety instructions (cont.)
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4
Extractors
Operating appliances that extract air to
the outside (extractor hoods, extractors,
air conditioning units, etc.) can create
negative pressure. If the boiler is oper-
ated at the same time, this can lead to a
reverse flow of flue gas.
Danger
The simultaneous operation of the
boiler and appliances that extract
air to the outside can result in life
threatening poisoning due to a
reverse flow of flue gas.
Fit an interlock circuit or take suita-
ble steps to ensure an adequate
supply of combustion air.
Safety instructions
Safety instructions (cont.)
5777267

5
1. Information Symbols ................................................................................................. 6
Spare parts lists ..................................................................................... 6
2. Commissioning, inspec-
tion, maintenance
Steps - commissioning, inspection and maintenance ............................ 7
3. Burner control unit Burner control unit LMO 64.301 ............................................................. 14
■Program sequence during commissioning ......................................... 14
■Function and fault indication by indicator light (LED) ......................... 15
■Burner fault flowchart .......................................................................... 17
4. Troubleshooting Diagnosis ............................................................................................... 18
■Fault indication with flash code ........................................................... 18
■Faults without flash code indication .................................................... 19
5. Component overview Component overview ............................................................................. 22
6. Connection and wiring dia-
gram
................................................................................................................ 24
7. Standard values for burner
adjustment
Standard values for burner adjustment .................................................. 25
■Notes regarding burner settings for room sealed operation ............... 25
8. Commissioning/service
reports
Report .................................................................................................... 27
9. Specification ................................................................................................................ 28
10. Final decommissioning Final decommissioning and disposal ..................................................... 29
11. Keyword index ................................................................................................................ 30
Index
Index
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6
Symbol Meaning
Reference to other document containing
further information
1.
Step in a diagram:
The numbers correspond to the order in
which the steps are carried out.
Warning of material losses and environ-
mental pollution
Live electrical area
Pay particular attention.
■Component must audibly click into place.
or
■Acoustic signal
■Fit new component.
or
■In conjunction with a tool: Clean the sur-
face.
Dispose of component correctly.
Dispose of component at a suitable collec-
tion point. Do not dispose of component in
domestic waste.
The steps in connection with commissioning, inspec-
tion and maintenance are found in the "Commission-
ing, inspection and maintenance" section and identified
as follows:
Symbol Meaning
Steps required during commissioning
Not required during commissioning
Steps required during inspection
Not required during inspection
Steps required during maintenance
Not required during maintenance
Spare parts lists
Information about spare parts can be found on the
Viessmann spare parts app.
Information
Symbols
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Information

7
Commissioning steps
Inspection steps
Maintenance steps Page
•1. Commissioning the system............................................................................................... 8
• • 2. Adjusting the air volume................................................................................................... 8
• • 3. Adjusting the oil pressure and checking the vacuum.................................................... 8
• • 4. Testing the burner and entering the actual values into the report................................ 10
• • 5. Shutting down the system
• • 6. Checking the firm seating of electrical connections
•7. Cleaning the burner........................................................................................................... 10
• • 8. Checking the impeller fixings
• • 9. Checking the flame tube fixings
•10. Replacing the nozzle.......................................................................................................... 11
• • 11. Checking and adjusting the mixing assembly................................................................ 11
•12. Fitting the burner cover on the burner casing
•13. Cleaning the oil pump filter and replacing it if required................................................. 12
•14. Replacing the filter element of the fuel oil filter
• • 15. Commissioning the system
• • 16. Checking the oil lines and connections for leaks
•17. Re-testing the burner and entering the actual values into the report
Commissioning, inspection, maintenance
Steps - commissioning, inspection and maintenance
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To obtain optimum combustion values, it is essential to
adjust the burner with the boiler at operating tempera-
ture (min. 60 °C).
c: The limits of the Swiss Clean Air Regulations
LRV 92 must be maintained.
Boiler control unit service instructions
Note
The Vitoflame 300 pressure-jet oil burner features very
good combustion values which are achieved without
the use of fuel oil additives (combustion improvers).
The use of combustion improvers that leave residues
is not permissible.
1. Check the heating system pressure and the oil
level in the tank.
2. Open the shut-off valves in the oil lines on the oil
tank and on the filter.
3. Fill the oil suction line and the filter with fuel oil
using a manual oil suction pump before switching
the burner on.
4. Switch ON the mains isolator (outside the installa-
tion room).
5. Switch ON the system ON/OFF switch at the con-
trol unit.
If the fault indicator on the control unit illuminates,
press the reset button on the burner (see chapter
"Function and fault indication by indicator light
(LED)").
Adjusting the air volume
The air volume is preset at the factory. Readjust the air
volume if necessary.
When commissioning the burner, some fine adjustment
may be required.
Before making adjustments, check whether inlet air
aperture C inside the casing is set to "8.0" (factory
setting).
Fig. 1
Fig. 2
1. Check the static burner pressure at test connector
B; to do so, remove the plastic cap.
Note
The actual static burner pressure must not vary
from the standard values: See chapter "Standard
values for burner adjustment".
2. If required: Adjust the static burner pressure at air
damper A:
Anti-clockwise turn:
■Higher static burner pressure
■More air
■Lower CO2 content
Clockwise turn:
■Lower static burner pressure
■Less air
■Higher CO2 content
Adjusting the oil pressure and checking the vacuum
The oil pressure is factory-set according to the oil
throughput. Readjust the oil pressure if necessary.
Commissioning, inspection, maintenance
Commissioning the system
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Fig. 3 Danfoss oil pump, type BFP 21 LE or LES,
or BFP 31 LE
Fig. 4 Suntec oil pump, type ALE 35
01. Switch off at mains isolator and safeguard against
reconnection.
02. Unscrew plug "P" A from the oil pump.
03. Unscrew plug "V" B from the oil pump.
Note
Place a suitable container below, to catch any oil
that may leak out.
04. Insert pressure gauge (measuring range 0 to
25 bar/2.5 MPa) and vacuum gauge (measuring
range 0 to 1 bar/0.1 MPa).
Note
Only seal in the pressure gauge and vacuum
gauge with copper or aluminium gaskets or with
O-rings. Never use sealing tape.
05. Start the burner.
Note
The solenoid valve opens.
06. Read off the oil pressure and vacuum of the pump
at the pressure gauge and vacuum gauge. The
vacuum must not exceed 0.3 bar/0.03 MPa at a
height difference of 3 m between the oil pump and
the bottom of the tank.
Note
Vacuum greater than 0.3 bar/0.03 MPa: Check the
filter for contamination and check the pipe run.
07. If necessary, adjust the oil pressure at oil pump
pressure setting screw C.
■Clockwise turn: Pressure rises
■Anti-clockwise turn: Pressure falls
Note
Only with Danfoss oil pump, type BFP 21 LE or
BFP 31 LE:
The LE nozzle shut-off function must be adjusted
at LE setting screw D (LE = ON), located on the
l.h. side of the oil pump.
Note
For standard values for burner adjustment, see
the chapter with the same title.
08. Test to check the actual emission values after
adjusting the oil pressure.
09. Switch system OFF at mains isolator and safe-
guard against unauthorised reconnection.
10. Undo the pressure and vacuum gauges.
Commissioning, inspection, maintenance
Adjusting the oil pressure and checking the… (cont.)
5777267

10
11. Check the plug seal rings for damage and replace
if necessary.
Insert plugs "P" A and "V" B.
12. Start the burner and check the plugs for leaks.
Testing the burner and entering the actual values into the report
Note
In the case of room sealed operation, observe the
information regarding burner adjustments in the chap-
ter with the same title.
Shutting down the system
Checking the firm seating of electrical connections
Cleaning the burner
For cleaning the combustion chamber and flues,
see boiler service instructions.
Fig. 5
1. Bring the burner into its maintenance position. 2. Clean casing, flame tube, mixing assembly B,
ignition electrodes A and impeller C.
Commissioning, inspection, maintenance
Adjusting the oil pressure and checking the… (cont.)
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11
Checking the flame tube fixings
Replacing the nozzle
Fig. 6
1. Place the burner cover with the blast tube connec-
tion facing upward on the burner casing (service
position). This prevents the formation of bubbles in
the blast tube connection.
2. Turn fixing screw B through two full turns to undo.
3. Remove mixing assembly A from the blast tube
connection.
4. Replace the nozzle (counterholding the blast tube
connection).
Note
For the make and type of nozzle, see Standard val-
ues for burner adjustment in the chapter of the
same title.
5. Push mixing assembly A onto the blast tube con-
nection as far as end-stop C (spacers) of the oil
preheater.
a
Fig. 7
6. Use suitably sized spacers C to adjust distance
"a" between the nozzles, in line with the table in
chapter "Checking and adjusting the mixing
assembly"
7. Retighten fixing screw B.
Checking and adjusting the mixing assembly
Check ignition electrodes A for wear, contamination
and dimensional accuracy (see diagram), and replace
if necessary.
Prior to installation, check sealing face D of baffle
plate B to the flame tube for damage and contamina-
tion.
Commissioning, inspection, maintenance
Checking the impeller fixings
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12
xxxxx
2.5
a
C A BB
D
Fig. 8
Rated heating output kW 18 22 27 33
Designation C VHG I-2 VHG I-3 VHG I-4 VHG I-5
Dimension a mm 2.5 6.5 2.0 5.0
Fitting the burner cover on the burner casing
Cleaning the oil pump filter and replacing it if required
Fig. 9 Danfoss oil pump, type BFP 21 LE / LES or
BFP 31 LE
AFilter plug
BO-ring (replace)
CFilter (replace)
Commissioning, inspection, maintenance
Checking and adjusting the mixing assembly (cont.)
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Fig. 10 Suntec oil pump, type ALE 35
AFilter (clean or replace)
BFlat gasket (replace)
CO-rings (replace)
DCover
Replacing the filter element of the fuel oil filter
Commissioning the system
Checking the oil lines and connections for leaks
Re-testing the burner and entering the actual values into the report
Commissioning, inspection, maintenance
Cleaning the oil pump filter and replacing it… (cont.)
5777267

14
!Please note
An incorrect burner control unit prevents the
burner from switching off when the set boiler
water temperature has been reached and can
cause damage to the burner. The burner is
locked out if the high limit safety cut-out
responds.
Only use burner control unit LMO 64.301.
Program sequence during commissioning
L
K
G
H
F
A B C D E
a
b
c
d
e
f
11
4
6
3
8
~
M
PTC
12
Fig. 11
AStart of oil preheat time
BStart-up begins
CPoint of flame formation
DOperating position
EControlled shutdown
§ to aS Screwless terminals at the burner control unit
FFlame monitor
GSolenoid valve on the oil pump
HHF ignition unit
KBurner motor
LOil preheater
a Oil preheat time up to 2 min*1
b Pre-ignition time approx. 15 s
c Pre-flushing time approx. 15 s
d Safety time max. 10 s
e Post-ignition time when flame
is established
approx. 3 s
f Post-flushing time approx. 90 s
Flame monitor sensor current
■Min. required 45 μA
■Max. permissible without flame 5.5 μA
Undervoltage
If the mains voltage drops below 165 V~, the burner
control unit initiates a safety shutdown. The system
restarts when the mains voltage rises above approx.
175 V~.
Note
If power supply is 2 × 127 V and red flash code: 10 x
flashing (see chapter "Faults with flash code indica-
tion"), contact your local Viessmann sales office.
Controlled intermittent operation
After a maximum of 24 hours non-stop operation, the
burner control unit initiates an automatic safety shut-
down with subsequent restart.
Control sequence in the event of faults
If a fault shutdown occurs, the outputs for the fuel
valves and the ignition system are immediately
switched off (< 1 s).
*1 Subject to the temperature of the fuel oil supplied.
Burner control unit
Burner control unit LMO 64.301
5777267
Functions

15
Cause Response
After a power failure Restart
After falling below the undervoltage level Restart
If there is a premature, faulty flame signal during pre-
flush time c
Fault shutdown at the end of pre-flush time c
If there is a premature, faulty flame signal during oil
preheat time a
Starting is prevented, fault shutdown after max. 40 s
If the burner does not light within the safety time TSA Fault shutdown at the end of the safety time TSA
If the flame fails during operation Max. 3 restarts, then fault shutdown
No heating or enabling of oil preheater within 10 min Fault shutdown
Fault shutdown
After a fault shutdown, the burner control unit remains
locked out (non-modifiable fault shutdown) and the red
indicator light illuminates. This state is also maintained
if the power supply fails.
Resetting the burner control unit
The system can be immediately reset after a fault shut-
down. Hold down the reset button for approx. 1 s
(< 3 s).
Ignition sequence
If the flame fails within the safety time, the system re-
ignites, but only until the end of the maximum safety
time. This allows several ignition attempts within the
safety time; see the above program sequence.
Repeat limitation
In the event of flame failure during operation, up to 3
re-ignition attempts can be made. The fourth flame fail-
ure during operation triggers a fault shutdown.
Counting of the repeats begins anew with each of the
following controlled starts:
■Via temperature controller or pressure regulator
■Via temperature limiter or pressure switch
■Via safety limiter
Function and fault indication by indicator light (LED)
During standard operation, the operating conditions
are indicated by colour codes at the end of reset but-
ton A (see the following table). The indicator perma-
nently illuminates red after a fault shutdown. In this
condition, the visual fault cause indication can be acti-
vated (see the following chapter "Burner fault flow-
chart").
Burner control unit
Burner control unit LMO 64.301 (cont.)
5777267
Functions

16
Fig. 12
1. Press reset button A for approx. 5 s (> 3 s) until
the signal lamp illuminates yellow.
2. A flash code is then shown as fault indication.
Meaning of the flash code: See the table in chapter
"Faults with flash code indication".
3. To reset the burner and exit the fault indication
function, press the reset button for approx. 1 s
(< 3 s).
LED colour Operating condition
Constant yellow Oil preheater active, oil preheat time a
Flashing yellow Ignition phase pre-purge, ignition activated
Constant green Operation, flame stable
Flashing green Operation, poor flame stability
Flashing yellow-red alternately Undervoltage (< 165 V)
Constant red Fault, burner locked out
Flashing red Fault indication with flash code (for meaning see chapter "Fault indica-
tion with flash code")
Green-red alternately External light before burner start
Flickering red Interface diagnosis
For diagnosis with interface adaptor (accessories)
Burner control unit
Burner control unit LMO 64.301 (cont.)
5777267
Functions

17
Burner fault flowchart
System cold
LED on burner control unit il-
luminates red
Reset burner control unit:
Press reset button for approx.
1 s (< 3 s)
Call up flash code:
Press the reset button for ap-
prox. 5 s (> 3 s) until the LED
switches to yellow
Call up data transfer for in-
terface (accessories):
■Press reset button for ap-
prox. 5 s (> 3 s): LED flash-
es red
■Press reset button again for
approx. 5 s (> 3 s): LED
flickers red
Burner start
Read off flash code and iden-
tify its meaning in the diagno-
sis table
Connect interface (see inter-
face operating instructions)
Remedy the fault Remedy the fault
Reset burner control unit:
Press reset button for approx.
1 s (< 3 s)
Reset burner control unit:
Press reset button for approx.
1 s (< 3 s)
Burner start Burner start
Burner control unit
Burner control unit LMO 64.301 (cont.)
5777267
Functions

18
Fault indication with flash code
Fault Red flash
code
Cause of fault Measure
Burner does not start (with
fault indication), indicator
light illuminates.
10 x Electrical connection faulty, wires
"L 1" and "N" interchanged or
burner control unit faulty.
Check the electrical connection.
If phases are correctly connec-
ted, replace burner control unit.
10 x External voltage at "S3" or "B4" Check the electrical connection
(see chapter "Connection and
wiring diagram").
Burner does not start (with
fault indication).
2 x Motor faulty Replace motor.
2 x Coupling between motor and oil
pump faulty
Replace coupling.
2 x Oil pump seized up or sluggish. Clean oil pump or replace it.
8 x Oil preheater faulty Replace oil preheater.
Burner starts, but no flame
is formed.
2 x Ignition electrodes incorrectly ad-
justed
Adjust correctly (see chapter
"Checking and adjusting the mix-
ing assembly").
2 x Ignition electrodes damp and
contaminated
Clean ignition electrode block.
2 x Insulation body of ignition electro-
des cracked
Replace ignition electrode block.
2 x Ignition transformer faulty Replace ignition transformer.
2 x Ignition cable faulty Replace ignition cable.
2 x Pump does not supply oil. Mount pressure gauge and vac-
uum gauge at the pump and
check build-up of pressure (see
following paragraph).
Burner starts; flame extin-
guishes during the start
phase
2 x Timer is faulty.
Fan motor does not temporarily
switch off when the solenoid
valve switches on.
Check the timer is working; re-
place if necessary.
2 x Recirculation gap set incorrectly Set recirculation gap correctly
(see chapter "Checking the recir-
culation gap" if included).
Pump does not supply oil. 2 x Shut-off valves closed at filter or
in oil line
Open valves.
2 x Filter blocked Clean filters (fuel oil filter and
pump filter), replace if necessary.
2 x Coupling between motor and
pump faulty
Replace coupling.
2 x Leak in suction line or filter bowl Retighten fittings. Check oil lines
and connections for leaks and
tighten if required.
2 x Oil flow and return hoses inter-
changed.
Correct the connections in line
with the marking on the pump.
2 x Vacuum in suction line too high
(above 0.3 bar)
Check sizing of oil line cross-sec-
tion. Replace filter. Check exter-
nal fuel oil valve.
2 x External anti-lift valve is faulty. Check external anti-lift valve; re-
place if necessary.
Troubleshooting
Diagnosis
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Diagnosis

19
Fault Red flash
code
Cause of fault Measure
Fan motor faulty 2 x Fan motor occasionally does not
start, due to faulty auxiliary wind-
ing or capacitor.
Replace the motor or capacitor.
Burner starts, but no oil is
injected.
2 x Solenoid valve coil is faulty. Replace solenoid valve coil.
2 x Oil pump is faulty. Replace oil pump.
2 x Nozzle is blocked. Replace nozzle.
External light during the
pre-purge phase
4 x Oil pump solenoid valve fails to
close.
Replace oil pump.
4 x Ignition electrodes incorrectly ad-
justed or worn
Check ignition electrodes; re-
place if necessary.
Burner starts and flame
builds, but burner enters
fault state after safety time
expires.
2 x Burner control unit faulty Replace burner control unit.
2 x Carbon deposits on flame tube or
mixing assembly
Clean flame tube and mixing as-
sembly.
Flame tears off during op-
eration
7 x Air in suction line Seal line and filter.
7 x Flue gas recirculation Check the flue. Carry out annular
gap test.
7 x Condensate backup Check condensate drain.
7 x Nozzle faulty Replace nozzle.
7 x Incorrect burner setting Check the default settings in line
with chapter "Standard values for
burner adjustment".
7 x Sensor plate contaminated Clean sensor plate.
Ignition switches on during
operation
7 x Sensor plate contaminated Clean sensor plate.
7 x Nozzle contaminated or faulty Replace nozzle.
7 x Condensate backup in flue gas
heat exchanger
Clean siphon and neutralising
system.
7 x Heating surfaces of flue gas heat
exchanger are contaminated
Clean the heating surfaces of the
flue gas heat exchanger.
!Please note
An incorrect burner control unit prevents the
burner from switching off when the set boiler
water temperature has been reached and can
cause damage to the burner. The burner is
locked out if the high limit safety cut-out
responds.
Only use burner control unit LMO 64.301.
Faults without flash code indication
Fault Cause of fault Measure
Burner does not start (no
fault indication), indicator
light does not illuminate.
No power Check fuse or plug-in connector aBÖ in
the control unit, check electrical connec-
tions, check position of the system
ON/OFF switch on the control unit and of
the mains isolator.
High limit safety cut-out has responded. Press the reset button at the boiler con-
trol unit.
Troubleshooting
Diagnosis (cont.)
5777267
Diagnosis

20
Fault Cause of fault Measure
Flame pulsates, tears off. Fan pressure too high Check the static burner pressure at the
test connector on top of the fan casing
(U-tube pressure gauge). Adjust the air
damper and blast tube connection so that
the lower static burner pressure (see
chapter "Standard values for burner ad-
justment") is not exceeded.
CO2 content too low Check the setting.
Excessive oil throughput Set the oil pressure correctly (see chapter
"Standard values for burner adjustment").
Condensate backup in flue gas heat ex-
changer
Clean siphon and neutralising system.
On-site condensate drain blocked Clean condensate drain.
Condensate lifting pump (if installed)
faulty
Replace condensate lifting pump.
Heating surfaces of boiler or flue gas
heat exchanger dirty
Clean heating surfaces of boiler or flue
gas heat exchanger.
In balanced flue operation, flue gas is
drawn in via the annular gap in the flue
system.
Test annular gap (measure directly at
burner connection adaptor). If flue gas is
detected, remedy the leak in the flue sys-
tem.
Immediate remedy: Temporarily operate
the burner in open flue mode.
If other combustion equipment is con-
nected to the same chimney, flue gas
may also be drawn in.
Observe installation regulations.
Flue gas from other combustion equip-
ment is drawn in via annular gap.
Extend flue on site, for example.
Nozzle faulty Replace nozzle.
Burner sooty; higher CO
concentration in flue gas.
Insufficient or too much air Correct the settings. Check and clean im-
peller.
Check ventilation in installation room.
Insufficient chimney draught Check chimney and flue gas routing.
Nozzle faulty Replace the nozzle, fit the right nozzle
(see chapter "Standard values for burner
adjustment").
Flue gas in the combustion air supply Check the flue system for tightness.
Insufficient combustion air supply Check combustion air supply.
In balanced flue operation, flue gas is
drawn in as well.
Check flue system.
Condensate backup in flue gas heat ex-
changer
Clean siphon and neutralising system.
CO2 content too low Incorrect setting Check setting (see chapter "Standard val-
ues for burner adjustment").
Infiltrating air Seal flue pipe at boiler flue connection.
Retighten screws on the boiler door and
on the flue outlet cover.
Troubleshooting
Diagnosis (cont.)
5777267
Diagnosis